A learning support system using a mobile computer has been developed for children. A SHARP's "Zaurus", pen-based interface which was available to input data, was selected for the system. As a mobile computer "Zaurus" was originally developed for office workers, it was difficult for children to use. In order to solve this problem a tailored program using "ADDIN tool kit" was developed.By using this learning support system, students are1) able to gather information easily outdoors2) able to exchange their data easily each othre3) able to expand their curiosity.